Lean-burn engines are known for their characteristic high levels of NOx emissions. The company says the new D-4 uses a high degree of exhaust gas recirculation(EGR)--as much as 40% when the engine operates in the lean combustion mode--and the natural eGr- like operation of the WT-i system to drastically reduce NOx production The new 3-way catalyst uses a storage/reduction design to purify occluded NOx at the stoichiometric level --When the engine operates in lean modes excess nox is stored until it can be combined/purified with exhaust gases produced during stoichiometric operation The new engine relies on powerful, precise engine management software to accurately tailor fuel-injection timing and duration. At high loads, such as during heavy acceleration, fuel is injected earlier in the compression stroke creating a homogeneous mixture and optimum powerLean-burn engines are known for their characteristic high levels of NOX emissions. The company says the new D-4 uses a high degree of exhaust gas recirculation (EGR)--as much as 40% when the engine operates in the lean￾combustion mode--and the natural EGR-like operation of the VVT-i system to drastically reduce NOX production. The new 3-way catalyst uses a storage/reduction design to purify occluded NOX at the stoichiometric level -- when the engine operates in lean modes, excess NOX is stored until it can be combined/purified with exhaust gases produced during stoichiometric operation. The new engine relies on powerful, precise engine￾management software to accurately tailor fuel-injection timing and duration. At high loads, such as during heavy acceleration, fuel is injected earlier in the compression stroke, creating a homogeneous mixture and optimum power